Internal combustion engines exhaust various pollutants. Diesel engines in particular produce sulfurous gases, aldehydes, nitrogen oxides, unburned hydrocarbons and other particulate matter. Aside from the general ecological interests in reducing such pollution, the necessity of doing so in underground mine environments is critical to the safety of the mine personnel. Further, in underground coal mines the high temperatures of exhaust gases present additional hazards. For instance, either the hot gases themselves or hot machine parts such as the manifold could ignite any combustible material present, such as coal dust. There is also the danger of miners working in the very confined area being burned by the hot gases.
Accordingly, various attempts have been made heretofore to provide a scrubber which would effectively clean and cool diesel exhaust in mine applications. Some of these devices are shown in British Pat. Nos. 1,010,415; 903,493; 706,129; 664,317; and 466,321.
In general, the prior art devices use water to remove the pollutants from the gas stream by one of two methods. In one approach, water is sprayed into the gas stream to scrub out the particulate. With water spray systems it is usually necessary to flow the gases along a tortuous path to effect adequate scrubbing and separation of the water out again. In the other popular approach, the exhaust gases are bubbled through a water bath. Both these methods substantially increase the back pressure on the engine and therefor actually reduce its effective horsepower.
British Pat. No. 1,010,415 shows a third approach in which the gases are flowed through a venturi tube and water droplets sucked into the gas flow from a water chamber below the venturi. A particular problem with this approach is that the effectiveness of the device is very sensitive to the level of the water.
In many of these prior art devices, the mixing action is inadequate to effect satisfactory cleaning of the gases. In addition, many of these devices emit gases which still include water droplets. Not only does this create problems with wet equipment and environment, the resultant steam haze restricts the mine operator's visibility. Furthermore, in underground mining applications the higher consumption of water of those devices requires additional storage capacity on the equipment.
To satisfy an additional concern in underground coal mining, where highly combustible methane gas and coal dust are present, a suitable scrubber should effectively arrest any exposed flame accompanying the engine exhaust.